Fetal magnetic resonance imaging, ultrasound, and echocardiography findings in twin reversed arterial perfusion sequence.

BACKGROUND: Twin reversed arterial perfusion (TRAP) sequence is a rare complication of monochorionic multiple gestation pregnancies, in which the pump twin provides hemodynamic support to a nonviable co-twin (acardius). Fetal magnetic resonance imaging (MRI) is used to detect pump twin abnormalities, particularly brain ischemia, prior to fetal intervention to interrupt umbilical blood flow to the acardius. OBJECTIVE: To summarize the imaging findings of TRAP sequence pregnancies in a large series. MATERIALS AND METHODS: A single-center retrospective review was performed of all TRAP sequence pregnancies referred for fetal MRI (2004-2021). Fetal MRI, ultrasound, and echocardiography data were collected. RESULTS: Eighty-eight TRAP sequence pregnancies with MRI were included (mean gestational age, 19.8±2.8 weeks). Demise of the pump twin was noted in two pregnancies at the time of MRI. By MRI, 12% (10/86) of live pump twins had abnormalities, including 3% (3/86) with brain abnormalities and 9% (8/86) with extra-cranial abnormalities. By echocardiography, 7% (6/86) of pump twins had structural cardiac abnormalities. Three acardius morphological subtypes were identified by MRI: acephalus (55%, 48/88), anceps (39%, 34/88), and amorphous (7%, 6/88). The mean ultrasound acardius to pump twin ratio A/P ratio, calculated for each twin pair as the ratio of the acardius trunk (and head, if present) plus limb volume to the pump twin estimated fetal weight) differed among the three acardius subtypes (P=.03). The mean A/P ratio moderately correlated with pump twin cardiothoracic ratio and combined cardiac output (Pearson's r=0.45 and 0.48, respectively, both P<.001). CONCLUSION: Fetal MRI of TRAP sequence pregnancies found anomalies in a substantial number of pump twins. The three acardius subtypes differed in A/P ratio, which moderately correlated with the pump twin cardiothoracic ratio and combined cardiac output.

Metastatic Giant Cell Tumor Causing Small Bowel Intussusception on 18 F-FDG PET/CT.

ABSTRACT: An 89-year-old man with a history of a malignant giant cell tumor of soft parts in the right thigh with recurrent/metastatic tumor in the right pelvis was found to have pulmonary nodules concerning for metastatic disease. Subsequent PET/CT unexpectedly demonstrated a right lower quadrant intussusception with a hypermetabolic mass serving as a lead point. Pathology of the resected mass causing the intussusception was compatible with a metastasis from the patient's malignant giant cell tumor of soft parts.